Aircrafts are provided with flight control surfaces including primary control surfaces formed as rudder faces such as ailerons, rudders, or elevators and secondary control surfaces such as flaps or spoilers. Flight control surface driving units for driving these flight control surfaces are provided with an actuator mounted on a flight control surface and an aircraft reaction link swingably connected to the actuator and the flight control surface.
For reducing the weight of aircrafts, many aircraft components made of metal materials such as titanium alloys are being replaced with those made of fiber-reinforced plastics. Among these components, some reaction links are known to be made of fiber-reinforced plastics instead of metal materials (see Japanese Patent Application Publication No. 2014-237429).
One example of such aircraft reaction links is the reaction link 200 shown in FIG. 19a, which includes a link body 210 connecting between a flight control surface and an actuator and bushes 220 for slidably supporting a connection shaft of the actuator. The link body 210 is made of a fiber-reinforced plastic. The bushes 220 are connected to the end portions of the link body 210 via fasteners 230. More specifically, each of the end portions of the link body 210 has a pair of planar plates. Each pair of planar plates 211 has a through-hole 212 into which a fastener 230 is inserted (see FIG. 19b). The bush 220 is partly inserted between the pair of planar plates 211. A fastener 230 is inserted into the through-hole 212 to fasten the bush 220 and the pair of planar plates 211 together.
The end portion of the link body 210 includes first fibers 241 and second fibers 242. The first fibers 241 extend in a first direction DR1 in which the link body 210 extends as shown in FIG. 19b. The second fibers 242 extend in a second direction DR2 orthogonal to the first direction DR1. However, since the pair of planar plates 211 have a through-hole formed therein, the first fibers 241 of the link body 210 in the shaded region in FIG. 19b are cut by the through-hole 212 and thus cannot withstand the tensile load imparted on the bush 220 (the load imparted in the direction of the white arrow in FIG. 19b). Therefore, the tensile load imparted on the bush 220 is withstood mainly by the second fibers 242 positioned more distally in the end portion of the link body 210 than the through-hole 212.
To overcome such a problem, conventional aircraft reaction links have been configured to increase the number of layers of the second fibers 242 positioned more distally in the end portion of the link body 210 than the through-hole 212 or increase the area of a part of the end portion more distal than the through-hole 212, so as to increase the supporting force for the bush 220. However, in the conventional aircraft reaction links, the end portion of the link body 210 has a larger size, resulting in a larger weight of the reaction link. Such a defect is not specific to aircraft reaction links but is common to supporting structures for force transmission members in which a force transmission member such as a bush for transmitting a force is supported by a fiber-reinforced plastic.